As is known, in the last few years there has been an increasing need for enabling recycling of the waste bituminous material deriving from the processes of production or use of products made with bituminous materials, such as, for example, bituminous membranes, bituminous films, bituminous tiles, and other bitumen-based materials typically used in the building sector.
For this purpose machines have been devised, which are able to fragment the waste bituminous material into granules of small dimensions, which are then re-used in processes for the production of new bitumen-based products of the type mentioned above.
The fragmentation into granules of the waste bituminous material carried out by the aforesaid machines is currently performed through a so-called “hot process”, which basically envisages a step of heating the bituminous waste inside a high-temperature heating chamber in such a way as to obtain a softening of the waste material, which passes from a solid state to a semisolid state, and of feeding the semisolid material thus obtained to a rotating cutting head, which fragments the semisolid waste into semisolid granules. Following upon the aforesaid operations, the semisolid granules are brought into the solid state via a step of cooling thereof.
Methods and machines of the type described above present the technical problem of being far from efficient from the standpoint of energy consumption. In fact, the need to heat the heating chamber and to subsequently cool the semisolid granules requires an absorption of a particularly high electrical power by the machine, said absorption giving rise as a whole to a relatively high consumption of electrical energy.
In addition, in the methods and machines referred to above the fragmentation into granules of the waste bituminous material with a polyester substrate is frequently incomplete. In fact, heating of the polyester layer determines formation of plastic filaments that prove difficult to separate from the rotating head and consequently keep some granules joined together following upon cooling thereof, thus giving rise to bituminous conglomerates of relatively large dimensions.
EP1236790 discloses a method for producing pellets by using waste plastics, as a raw material which is injected into a blast furnace, a cement kiln, or the like.